In resent years, a leakage current has not been able to be ignored in a semiconductor device (semiconductor integrated circuit) such as an LSI according to microfabrication of process technique. Japanese Laid-open Patent Publication No. 2003-209616 discloses power gating (PG) technique of which power to a block is on/off-controlled has been applied in order to reduce leakage electric power by cutting off power supply to the block not in use inside the semiconductor device.
In applying the power gating technique to the semiconductor device, a power switch to switch whether or not to perform power supply to an internal power domain (the block) is controlled by a power management unit (PMU).
Further, Japanese Laid-open Patent Publication No. 2006-344640 discloses when power of a first power domain inside a semiconductor device is off, power of a second power domain where a signal from a circuit in the first power domain is input is made to be on, and thereby, an indefinite value signal including an intermediate potential is led to be applied to a circuit in the second power domain. As a result, the circuit in the second power domain operates erroneously, and an unintended leakage current (a short-circuit current) flows therethrough. Accordingly, when the plurality of power domains exist, providing a circuit to prevent the indefinite value signal from propagating, and a rule regarding the sequence of supplying power (start sequence) are to be needed.
Thus, power control specification such that how the power domains inside the semiconductor device are configured, or in what sequence power is supplied (the start sequence), or the like differs in each of the semiconductor devices, and therefore, a design for the power management unit fitting specification is needed by each of the semiconductor devices. However, in the case when the number of products of the semiconductor device to which the power gating technique is applied increases, and in the case when the power gating technique is applied to an ASIC (Application Specific Integrated Circuit) and a COT (Customer Owned Tooling) business, designing the power management unit suitable for the specification of each of the products by every product development results in a significant problem in terms of development efficiency and design man-hours.